The present invention relates to check valves and more particularly to a check valve having a removable seat portion.
Check valves are placed in fluid flow lines to allow the flow of fluids in one direction but block the reverse flow. See, e.g., U.S. Pat. Nos. 2,419,318; 2,482,198; 2,767,735; 3,058,534; 3,066,693; 3,363,645; 3,509,908; 3,565,107; 3,612,097; 3,720,228; 3,817,277; 3,933,173; 3,990,471; 4,061,535; 4,128,111; and 4,201,241; British Pat. No. 1,214,619; and French Pat. Appln. No. 2,216,496.
Some of those documents mention or discuss check valves having removable seats. See, e.g., U.S. Pat. Nos. 3,363,645; 4,128,111; and 4,201,241. Some of those documents mention or discuss means for creating a tight seal between the flapper of the valve and the valve seat when the valve is in the closed position. See, e.g., U.S. Pat. Nos. 3,612,097; 3,817,277; and 4,201,241; and French Pat. Appln. No. 2,216,496. U.S. Pat. No. 3,066,693 refers to a flapper having a recess for reducing the wear and erosion of the flapper. Check valves having valve bodies capable of being opened from the top for removal of the flapper are known.
A continuing problem with check valves, particularly those used with fluids containing abrasive particles, is the time and expense required to smooth (e.g., by grinding) or in some cases to replace the valve seats when replacing the flappers alone will not restore fluid tight seals to the valves. In known valves, at least one connection of each valve to its pipelines must be broken to allow access to the valve seat for such repair or replacement.